a
: a narrow elongated tract extending from a focus of suppuration and serving for the discharge of pus
b(1)
: a cavity in the substance of a bone of the skull that usually communicates with the nostrils and contains air
(2)
: a channel for venous blood
(3)
: a dilatation in a bodily canal or vessel
c
: a cleft or indentation between adjoining lobes (as of a leaf or corolla)
Examples of sinus in a Sentence
Recent Examples on the Web
The best down alternative pillows, however, are popular for resembling down without the dust and mites that can often wreak havoc on sinuses overnight.
—
Julia Harrison, Architectural Digest, 24 Oct. 2025
Potential complications include sinus and ear infections; inflammation of the heart, brain or muscle tissues; multi-organ failure; sepsis or the worsening of chronic conditions like asthma.
—Mary Walrath-Holdridge, USA Today, 23 Oct. 2025
Some had a fungal infection called mucormycosis, also known as black fungus, which can infect the nasal passages, sinuses, lungs and skin of people who have chronic high blood glucose or are immunocompromised.
—Carrie Arnold, Scientific American, 14 Oct. 2025
Star Clooney was unable to attend the film’s press conference and premiere due to a sinus infection.
—Natalie Oganesyan, Deadline, 29 Sep. 2025
See All Example Sentences for sinus
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Julia Harrison, Architectural Digest, 24 Oct. 2025
Potential complications include sinus and ear infections; inflammation of the heart, brain or muscle tissues; multi-organ failure; sepsis or the worsening of chronic conditions like asthma.
—Mary Walrath-Holdridge, USA Today, 23 Oct. 2025
Some had a fungal infection called mucormycosis, also known as black fungus, which can infect the nasal passages, sinuses, lungs and skin of people who have chronic high blood glucose or are immunocompromised.
—Carrie Arnold, Scientific American, 14 Oct. 2025
Star Clooney was unable to attend the film’s press conference and premiere due to a sinus infection.
—Natalie Oganesyan, Deadline, 29 Sep. 2025
See All Example Sentences for sinus
Cite this Entry
“Sinus.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/sinus. Accessed 30 Oct. 2025.
Copy CitationKids Definition
Medical Definition
sinus
noun
si·nus
ˈsī-nəs 
: a cavity or hollow in the body: as
a
: a narrow elongated tract extending from a focus of suppuration and serving for the discharge of pus
a tuberculous sinus
b(1)
: a cavity in the substance of a bone of the skull that usually communicates with the nostrils and contains air
(2)
: a channel for venous blood
(3)
: a dilatation in a bodily canal or vessel
Love words? Need even more definitions?
Merriam-Webster unabridged
Share